118 Origin of New Fomis in Hieracium 



are probably old, species of a restricted range may be old or may have 

 newly arisen. In the former case they are to be considered as dying-out 

 species and have usually a rather isolated position from a systematical 

 point of vieAv ; the Archieracium microspecies can scarcely be included 

 in this category. They must most naturally be considered as newly 

 arisen species of restricted range. 



A Swedish botanist, G. Samuelsson, has in a paper (1910) given the 

 geographical range of some Hieracia from the middle of the Scandinavian 

 peninsula. He shows that some of them have a very restricted area of 

 occurrence, mostly with a centre where they are most common and from 

 which they radiate becoming less and less common towards the periphery. 

 These microspecies are usually closely related to others which have a 

 somewhat wider distribution, and Samuelsson considers the former as 

 derived from the latter. 



I think his supposition is right, and starting from this idea I tried 

 to get new forms in my cultures by making them as extensive as 

 possible. I thought that there would be a chance that between a large 

 number of uniform individuals single diverging individuals might appear. 

 This is the same method as that used by H. de Vries in his first Oenothera 

 Lamarckiana experiments. 



Therefore I sowed as many seeds as possible of several rather widely 

 distributed forms which were tried before by culture after agamization^ 



Each form was constant and produced uniform offspring and apoga- 

 mically. Each of these new cultures came from seeds of one individual 

 and only from agamized heads. In the four first experiments I got from 

 100 to 300 plants ; the seeds were sown in 1910 and the plants flowered 

 in 1911. In three of the experiments all the plants were uniform and 

 like their parent, but in the fourth experiment, a H. rigidum Fr. {H. 

 tridentatum) which originally came from a wood near Svendborg, Denmark, 

 I got 154 plants, 153 of which were normal, while one was different in 

 several respects. Some flowerheads of this individual were agamized in 

 1911, the seeds sown in 1912 and the new generation flowered in 1913. 

 All the plants of this generation were uniform and like their parent, 

 thus different from the original H. rigidum. I have later repeated the 

 agamization and sown the seed twice (1912-13 and 1915-16) and ob- 

 tained the same result. 



The new form — I call it H. rigidum Beta — was thus at once constant 



' By the terms " agamization " and " agamize " I mean the process of I'emoving the 

 anthers and the stigmas by means of a cut with a razor before the opening of the flowers 

 of a flower head (the prefix a and the word yd/xos, marriage). 



